1. Field of the Disclosure
The present disclosure relates to a capacitance-type detecting device that detects an object to be detected using a capacitance variation, and more particularly, to a capacitance-type detecting device that detects the coordinates of an object to be detected in a detection target region.
2. Description of the Related Art
Capacitance-type touch panels have been proposed as input devices of various apparatuses (for example, see U.S. Pat. No. 4,550,221). The touch panel includes a plurality of detecting electrodes, which are provided in a houndstooth pattern on a sensor substrate such that a capacitance is formed between adjacent electrodes. The detecting electrodes have a substantially rhombic shape in a plan view and include X-axis electrodes, which are connected in series to each other in the X-axis direction in the sensor surface, and Y-axis electrodes, which are connected in series to each other in the Y-axis direction perpendicular to the X-axis direction in the sensor surface. When the operator presses any position of the sensor surface on a touch panel with the finger, some of the electric field lines formed between a plurality of detecting electrodes are drawn out by the finger and the capacitance formed between the detecting electrodes is reduced. Signals are output from the X-axis electrodes and the Y-axis electrodes according to a variation in the capacitance between the detecting electrodes and are sequentially detected from one end to the other end in the X-axis direction and the Y-axis direction, thereby detecting the touch position of the finger of the operator in the sensor surface.
However, in the capacitance-type touch panel according to the related art, since the plurality of detecting electrodes with the same shape are arranged on the sensor substrate, the capacitance between the detecting electrodes formed at the edge of the sensor substrate is less than that between the detecting electrodes formed at the center of the sensor substrate. Therefore, a capacitance variation when the finger of the operator presses the edge of the sensor substrate is less than that when the finger of the operator presses the center of the sensor substrate, and detection sensitivity at the edge of the sensor substrate is less than that at the center of the sensor substrate.
Therefore, in the capacitance-type touch panel according to the related art, when the touch panel is designed using the capacitance variation at the center of the sensor substrate as a reference, it is difficult to accurately detect the finger of the operator which touches the edge of the sensor substrate. On the other hand, when a predetermined threshold value is set using the capacitance variation at the edge of the sensor substrate as a reference, a detection error (the object to be detected is detected in a state in which the object to be detected does not touch the sensor surface) occurs in the center of the sensor substrate. In particular, when multi-point detection is performed to detect all of a plurality of objects to be detected, it is difficult to accurately detect both an object to be detected which approaches the edge of the sensor substrate and an object to be detected which approaches the center of the sensor substrate.